The cerebellum, which is an important brain site for control of muscle function, has been implicated in two aspects of epilepsy. First, intoxication with diphenylhydantoin leads to cerebellar signs and after prolonged exposure, neuropathological changes. Second, several reports indicate that anticonvulsant materials can activate cerebellar Purkinje cells which then exert an antiseizure effect. We plan to continue our investigations into the mode of anticonvulsant drug actions on the cerebellum and to delinate the role of the cerebellum in experimentally-induced convulsive seizures. In a related program we wish to explore the influence of drugs on motor function. We will examine peripheral proprioceptor mechanisms and their modification by neurally active substances. We will also evaluate drugs on spastic muscle conditions produced by upper motor neuron lesions. We plan to analyze sites and mechanisms of drug action to alleviate spastic muscle conditions.